Sole structure of athletic shoe

ABSTRACT

The present invention relates to a sole structure of an athletic shoe and its object is to effectively absorb a shock applied to a shoe heel portion directly after landing and to prevent pronation or supination after landing. The sole structure of the athletic shoe according to the present invention includes an upper midsole ( 3   a ) that is formed of a soft elastic material and that extends from the heel portion to a forefoot portion of a shoe through a midfoot portion, a lower midsole ( 3   b ) that is formed of a soft elastic material and that is disposed at least at the heel portion under the upper midsole ( 3   a ), a wavy plate ( 4 ) that is inserted between the upper and lower midsoles ( 3   a   , 3   b ) and that has a wavy corrugation at least at the heel portion, which progresses from the rear end side of the heel portion to the midfoot portion, an outsole ( 5 ) fitted to the bottom surface of the lower midsole ( 3   b ), and a shock absorbing member ( 7 ) provided at a heel strike region of the heel portion between the wavy plate ( 4 ) and the outsole ( 5 ).

This is a 371 of PCT/JP00/03801 filed on Jun. 12, 2000.

TECHNICAL FIELD

The present invention relates to a sole structure of an athletic shoe,and more particularly, a sole structure that has a wavy plate insertedbetween an upper midsole and a lower midsole.

BACKGROUND OF THE INVENTION

A sole for an athletic shoe used in various sports includes a midsoleand an outsole that is fitted on the bottom surface of the midsole anddirectly contacts the ground. The midsole is generally formed of a softelastic material to ensure adequate cushioning properties as a shoe.

Incidentally, as a sports shoe, not only cushioning properties but alsorunning stability is required. That is, there exists a need to preventexcessive lateral or transverse deformation of a sole, such as pronationor supination occurring at the time of striking onto the ground.

In order to prevent such a lateral deformation, as shown in Japanesepatent application laying-open publication No. 11-203, MizunoCorporation proposed a midsole structure having a wavy plate with acorrugation inserted thereinto. In this case, by the action of the wavyplate, a resistance force occurs to restrain a heel portion of a midsolefrom deforming in the transverse direction at the time of impacting ontothe ground, thereby preventing the heel portion of a shoe from laterallydeforming.

Such a wavy plate prevents lateral deformation of a shoe, but itdecreases cushioning properties of the whole midsole. In the midsolestructure shown in the above-mentioned publication, amplitude of acorrugation of a wavy plate is suitably varied between a front end and arear end or between a medial side and a lateral side of the shoe heelportion to achieve cushioning properties. Although such a method ofsecuring cushioning properties and preventing lateral deformation wasadequate for runners whose pronation or supination is not so great, butit was inadequate for runners whose pronation or supination is greater.In athletic sports, such as tracks, field events, tennis, volleyball,basketball, or the like, an impact load three to five times an athlete'sweight is applied on landing and especially on jumping, very high impactload about ten times an athlete's weight is applied. In these sports,adequate cushioning properties were not necessarily achieved by theabove-mentioned midsole structure.

The present invention has been made in view of these conventionalcircumstances, and its object is to provide a sole structure of anathletic shoe that can not only effectively absorb an impact loadapplied to a heel portion of the shoe directly after contacting theground but also securely prevent a pronation or supination of a shoewearer's foot.

SUMMARY OF THE INVENTION

A sole structure of an athletic shoe according to a first inventionincludes an upper midsole that is formed of a soft elastic material andthat extends from a heel portion of the shoe to a forefoot portionthrough a midfoot portion, a lower midsole that is formed of a softelastic material and that is disposed at least at the heel portion ofthe shoe under the upper midsole, a wavy plate or a corrugated sheethaving a wavy corrugation that progresses from a rear end side of theheel portion toward the midfoot portion and that is provided at least atthe heel portion between the upper and lower midsoles, an outsole thatis fitted on the bottom surface of the lower midsole, and a shockabsorbing member that is fitted at a “heel strike region” of the heelportion of the shoe between the wavy plate and the outsole.

Here, the term, “heel strike region” used herein means a region of theheel portion of a shoe that contacts the ground at a first stage oflanding when a shoe wearer lands on the ground from the heel portion ofthe shoe.

As a “shock absorbing member”, a high molecular compound havingviscoelasticity is preferable. Specifically, polystyrene, polyurethane,or polyisoprene elastomer may be utilized. Also, a blend type of thesemixed elastomers, or both solid and foamed types are included. The wavyplate is preferably formed of thermoplastic resin or thermosettingresin.

In this first invention, an impact load applied to the heel strikeregion of the shoe heel portion directly after contacting the ground iseffectively absorbed by the shock absorbing member fitted at the heelstrike region. And after landing onto the ground, pronation orsupination of a shoe wearer's foot is securely prevented by the actionof the wavy plate.

Also, in this case, because the shock absorbing member is providedbetween the wavy plate and the outsole, that is, on the side of thelower midsole, stability of the shoe heel portion on landing is securedto some extent by the upper midsole, and the impact load applied to theoutsole is absorbed by the shock absorbing member. In contrast, when theshock absorbing member is provided on the upper midsole side, that is,between the upper and the wavy plate, lateral deformation of the shoeheel portion is easy to occur on landing and stability of the shoe heelportion is hardly maintained.

In a sole structure of an athletic shoe according to a second invention,the shock-absorbing member is formed of a viscoelastic material having70% or more energy loss, or preferably, 85% or more energy loss.

Here, the term, “viscoelasticity” used herein means a phenomenon inwhich deformation caused by an external force appears as an overlap ofelastic deformation and viscous flow, and such properties are especiallyremarkably seen in high molecular compound.

When an impact force is applied to the viscoelastic material, a portionof supplied energy by the impact force is converted into heat energy andthe like, and by the amount of the converted energy, the impact force isabsorbed and a shock is relieved. On the other hand, the other portionof supplied energy, which is not liveried converted into heat energy andthe like, restores the deformed viscoelastic material to its originalcondition before deformation as a restoring energy by elastic rebound.In this case, the amount of supplied energy minus the restoring energyis an energy loss.

Generally, 70% or 85% or more energy loss is considerably high value.When a shock absorbing member formed of only a viscoelastic materialhaving such a high energy loss is provided in the midsole, a shoe wearerreceives a feeling of floating from the ground during activities,especially running, and as a result, he or she cannot exert a necessarykick power to the ground at the start of running and cannot controlactivities.

In contrast, according to the present invention, since such a shockabsorbing member is used with the wavy plate, compressive and lateraldeformations of the upper and lower midsoles after landing arerestrained by the action of the wavy plate. Thus, a shoe wearer canexert a sufficient kick force to the ground and control activities.

In other words, as in the present invention, that the wavy plate isprovided in the midsole enables to use the shock absorbing materialformed of a viscoelastic material having 70% or more, or 85% or morehigh energy loss.

According to the present invention, even in sports where very highimpact force is applied on jumping, a shock applied to the shoe heelportion is absorbed and relieved by the shock absorbing member having70% or more, or 85% or more high energy loss, and lateral deformation ofthe shoe heel portion is prevented and activities are controlled by theaction of the wavy plate.

In a sole structure of an athletic shoe according to a third invention,the shock absorbing member has hardness of 55 degrees or less,preferably, 45 degrees or less at Asker C scale. In this case, an impactforce applied to the shock absorbing member is absorbed by converting aportion of supplied energy by the impact force into heat energy and thelike. In addition, the reason why the hardness of 55 degrees or less atAsker C scale is employed is that less shock absorbing properties orless cushioning properties are acquired if the hardness is greater than55 degrees at Asker C scale.

In a sole structure of an athletic shoe according to a fourth invention,the shock absorbing member extends along the outer circumference of theshoe heel portion and has a width of 10(mm) or more.

Here, the reason why the width of the shock absorbing member is limitedto 10(mm) or more is that at least the width of 10(mm) is required toabsorb a shock directly after contacting the ground. And the reason whythe width over 10(mm) is allowed is that even when the shock absorbingmember has the width over 10(mm) the whole midsole can be prevented frombeing excessively compressed by the action of the wavy plate.

In a sole structure of an athletic shoe according to a fifth invention,there exist inequalities, 0.1L≦LL≦0.5L and LM≦0.1L.

Here, L: entire length of a horizontal projection plane of an outsole.

LL: length of a lateral side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

LM: length of a medial side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

In this case, since the lateral side region of the shock absorbingmember is longer than the medial side region thereof, a shoe solestructure, which is suitable for sports such as tracks where landingfrequently occurs on the lateral side, can be achieved.

Here, the reason why the elongated length LL of the shock absorbingmember is limited to 0.1L or more is that at least the length of 0.1L isrequired to absorb a shock directly after landing on the lateral side.The reason why the elongated length LL is limited to 0.5L or less is asfollows: It is sufficient that the shock absorbing member extends to themidfoot portion at the longest, and if the shock absorbing member hasthe length over 0.5L, it reaches the forefoot portion. Further, thereason why the elongated length LM is limited to 0.1L or less is that ifthe length is over 0.1L it promotes pronation.

In a sole structure of an athletic shoe according to a sixth invention,amplitude of a wavy configuration of the wavy plate at the heel portionis smaller on the lateral side and greater on the medial side. That is,moment of inertia of area of the wavy plate is greater on the medialside, and thus, compressive hardness, which represents hardness tocompressive deformation of the whole midsole, is higher on the medialside.

This sixth invention exercises a superior effect when it is combinedwith the fifth invention. That is, in sports such as tracks, when arunner lands on the ground from the lateral side of the heel portionduring running, the shock absorbing member on the lateral side absorbs ashock to the outsole directly after contacting the ground. And themedial side of the midsole having greater compressive hardness sustainsleaning of foot toward the medial side of the heel portion afterlanding. In such a way, by interaction between the shock absorbingmember and the wavy plate, a shock applied to the shoe heel portiondirectly after contacting the ground is effectively absorbed andpronation of a shoe wearer's foot is securely prevented.

In a sole structure of an athletic shoe according to a seventhinvention, there exist inequalities, LL≦0.1L and 0.1L≦LM≦0.5L.

Here, L: entire length of a horizontal projection plane of an outsole.

LL: length of a lateral side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

LM: length of a medial side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

In this case, since the medial side region of the shock absorbing memberis longer than the lateral side region thereof, a shoe sole structure,which is suitable for sports such as tennis or basketball where landingfrom the medial side and transverse movements frequently occur, can beachieved.

Here, the reason why the elongated length LM of the shock absorbingmember is limited to 0.1L or more is that at least the length of 0.1L isrequired to absorb a shock directly after landing on the medial side.The reason why the elongated length LM is limited to 0.5L or less is asfollows: It is sufficient that the shock absorbing member extends to themidfoot portion at the longest, and if the shock absorbing member hasthe length over 0.5L, it reaches the forefoot portion. Further, thereason why the elongated length LL is limited to 0.1L or less is that ifthe length is over 0.1L it promotes supination.

In a sole structure of an athletic shoe according to an eighthinvention, amplitude of a wavy configuration of the wavy plate at theheel portion is smaller on the medial side and greater on the lateralside. That is, moment of inertia of area of the wavy plate is greater onthe lateral side, and thus, compressive hardness, which representshardness to compressive deformation of the whole midsole, is higher onthe lateral side. This eighth invention exercises a superior effect whenit is combined with the seventh invention. That is, in sports such astennis, basketball, or the like, when a player lands on the ground fromthe medial side of the heel portion during a game, the shock absorbingmember on the medial side absorbs a shock to the outsole directly aftercontacting the ground. And the lateral side of the midsole havinggreater compressive hardness sustains leaning of foot toward the lateralside of the heel portion after landing. In such a way, by interactionbetween the shock absorbing member and the wavy plate, a shock appliedto the shoe heel portion directly after contacting the ground iseffectively absorbed and supination of a shoe wearer's foot is securelyprevented.

In a sole structure of an athletic shoe according to a ninth invention,there exist inequalities, 0.1L≦LL≦0.15L and 0.1L≦LM≦0.15L.

Here, L: entire length of a horizontal projection plane of an outsole.

LL: length of a lateral side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

LM: length of a medial side region of a shock absorbing member measuredfrom the rearmost end of the heel portion along the shoe elongateddirection.

In this case, since the medial side region of the shock absorbing memberhas almost the same length as the lateral side region thereof, a shoesole structure, which is suitable for sports such as walking wherelanding occurs on the central portion of the rear end side of the shoeheel portion, is achieved.

Here, the reason why each of the elongated lengths LL and LM of theshock absorbing member is limited to 0.1L or more is that at least thelength of 0.1L is required to absorb a shock directly after landing onthe rear central portion. The reason why each of the elongated lengthsLL and LM is limited to 0.15L or less is as follows: It is sufficientthat the shock absorbing member has the length of 0.15L at the longestto absorb a shock applied to the rear central portion, and if the shockabsorbing member has the length over 0.15L, it may promote pronation andsupination.

In a sole structure of an athletic shoe according to a tenth invention,amplitude of a wavy configuration of the wave plate at the heel medialportion is nearly equal to that of a wavy configuration of the wavyplate at the heel lateral portion. This tenth invention is suitable fora shoe such as a walking shoe where landing on the ground frequentlyoccurs on the general central portion on the rear end side of the shoeheel portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a running shoe employing a sole structureaccording to an embodiment of the present invention.

FIG. 2 is a lateral side view of the sole structure of FIG.1.

FIG. 3 is a medial side view of the sole structure of FIG. 1.

FIG. 4 is a top plan view of the sole structure of FIG. 1.

FIGS. 4A and 4B are top plan views like FIG. 4, but respectively showtwo alternative embodiments of the configuration of the shock absorbingmember.

FIG. 5 is a cutaway bottom view of the sole structure of FIG. 1.

FIGS. 5A and 5B are cutaway bottom views like FIG. 5, but respectivelyshow the alternative sole structures of FIGS. 4A and 48.

FIG.6 is a lateral side view of the wavy plate.

FIGS. 6A and 6B are lateral side views of a portion of the wavy platesimilar to FIG. 6, but relating to two alternative embodiments.

FIG. 7 is a medial side view of the wavy plate.

FIGS. 7A and 7B are medial side views of a portion of the wavy plate inthe alternative embodiments of FIGS. 6A and 6B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Explanation of theWhole Structure of Athletic Shoe

Here, a running shoe will be explained as an example of an athleticshoe. As shown in FIG. 1, a sole of an athletic shoe 1 includes an uppermidsole 3 a that extends from a heel portion to a forefoot portion ofthe shoe and that is fixed to a bottom portion of an upper 2, a lowermidsole 3 b that is disposed mainly at the heel portion of the shoeunder the upper midsole 3 a, a wavy plate or corrugated sheet 4 that hasa wavy corrugation and that is inserted between the upper midsole 3 aand the lower midsole 3 b, and outsole 5 that is fixed to the bottomsurfaces of the upper and lower midsoles 3 a, 3 b and that directlycontacts the ground, and a shock absorbing member 7 that is provided ata heel strike region between the wavy plate 4 and the outsole 5.

The upper midsole 3 a and the lower midsole 3 b are provided to relievea shock that is applied to the bottom portion of the shoe at the time oflanding, and they are generally formed of a soft elastic material havinggood cushioning properties. Specifically, thermoplastic synthetic resinfoam such as ethylene-vinyl acetate copolymer (EVA), thermosetting resinfoam such as polyurethane (PU), or rubber material foam such asbutadiene or chloroprene rubber is used.

The wavy plate 4 is preferably formed of thermoplastic resin such asthermoplastic polyurethane (TPU) of comparatively rich elasticity,polyamide elastomer (PAE), ABS resin or the like. Alternatively, thewavy plate 4 is formed of thermosetting resin such as epoxy resin,unsaturated polyester resin or the like. In addition, a plurality oftransversely extending holes 6 are formed at regions where the upper andlower midsoles 3 a, 3 b contact the wavy plate 4. These holes 6 areprovided to improve cushioning properties of the whole midsole and toreduce its weight.

The shock absorbing member 7 is provided to absorb and relieve a shockimmediately after contacting the ground, and a high molecular compound,or polymer having viscoelasticity is preferable. Specifically,polystyrene, polyplefin, polyurethane, polyester, polyamide, polydiene,polyisoprene, polyethylene, fluorine, or silicone elastomer may beutilized. Also, a blend type of these mixed elastomers, or both solidand foamed types may be included.

When the shock absorbing member 7 is formed using these elastomers,additives to the elastomers may be adjusted and an expansion ratio maybe varied to gain 70% or more energy loss, preferably 85% or more energyloss.

In another aspect of the present invention, as the shock absorbingmember 7, a member having hardness of 55 degrees or less, preferably 45degrees or less at Asker C scale is used. Here, the reason why thehardness is limited to 55 degrees or less at Asker C scale is that shockabsorbing properties or cushioning properties decreases if the hardnessis over 55 degrees.

Specified examples of the shock absorbing member 7 are shown below:

EXAMPLE 1

A formed polymer having a base polymer formed of 70 portion of “HYBRAR(trade mark)” of Kuraray Co., Ltd. that is polystyrene/polyisopreneelastomer, and 30 portion of isoprene rubber (IR). Hardness is 40degrees at Asker C scale; specific gravity is 0.31; 89% energy loss,which is measured by Mizuno Corporation.

EXAMPLE 2

“Sorbothane (trademark)” that is polyurethane elastomer of SanshinEnterprises Co., Ltd. Hardness is 41 degrees at Asker C scale; specificgravity is 1.37; 80% energy loss, which is measured by MizunoCorporation.

The above-mentioned examples are mere ones and various compositionsother than the above-mentioned ones may be employed by suitably changingkinds of elastomers and kinds or amounts of the additives introducedthereinto.

Explanation of Sole Structure

The sole structure of the running shoe 1 will be explained hereinafterby using FIGS. 2 to 7. As shown in FIGS. 2 to 4, the wavy plate 4extends from a heel part A of the shoe to a rear end portion,of aforefoot part C through a midfoot part (or plantar arch part) B. Thewavy plate 4 includes a heel portion 4 a formed with a wavy corrugationthat progresses from the rear end side of the heel part A to the frontend side, and a midfoot portion 4 b in the shape of generally flat platethat is integrally formed with the heel portion 4 a. Dotted linesextending in the transverse direction at the heel portion 4 a in FIG. 4indicate crest lines or trough lines of a wavy corrugation of the wavyplate 4.

In the case of a shoe (not shown) where the wavy plate 4 extends towardthe front end of the forefoot part C, the lower midsole 3 b also extendstoward the front end of the forefoot part C, correspondingly to the wavyplate 4.

As shown in FIGS. 6 and 7, amplitude of a wavy corrugation of the wavyplate 4 is AL on the lateral side and AM on the medial side, and thereexists an inequality, AM>AL.

In addition, the wavy plate 4 is formed with flanges 41, 42 protrudingupwardly and downwardly These flanges 41, 42 are provided only at theboth edges of the medial and lateral sides of the heel part A and arenot provided between the both edges of the medial and lateral sides ofthe heel part A. Therefore, each of the flanges 41, 42 is not directlyrelated to amplitude of a wavy corrugation of the wavy plate 4, but byproviding these flanges 41, 42, lateral or transverse deformation of theupper midsole 3 a is further restrained.

As shown in FIGS. 4 and 5, the shock absorbing member 7 extends as acurved strip along the outer circumference of the shoe heel part A andis disposed at a heel strike region of this running shoe 1, or rear endportion of the heel part A. The shock absorbing member 7 in the shape ofa curved strip has a width W, which satisfies an inequality, W≧10(mm).

Here, the reason why the width of the shock absorbing member is limitedto 10(mm) or more is that at least 10(mm) is required to absorb a shockimmediately after contacting the ground. And the reason why the widthover 10(mm) is allowed is that even when the shock absorbing member hasthe width over 10(mm) the whole midsole can be prevented from beingexcessively compressed at the time of landing by the action of the wavyplate 4.

Furthermore, there exist inequalities, 0.1L≦LL≦0.5L and LM≦0.1L.

Here, L: entire length of a horizontal projection plane of the outsole5.

LL: length of a lateral side region of the shock absorbing member 7measured from the rearmost end of the heel portion along the shoeelongated direction.

LM: length of a medial side region of the shock absorbing member 7measured from the rearmost end of the heel portion along the shoeelongated direction.

In other words, the laterally extending portion LL is 10 to 50% of theentire length L, and the medially extending portion LM is less than orequal to 10% of the entire length L.

Then, function and effect of this embodiment will be described. A shockapplied to the heel strike region of the shoe heel part A directly afterstriking onto the ground during running is effectively absorbed andrelieved by converting a portion of energy by the shock into heat energyand the like through the shock absorbing member 7 fitted at the heelstrike region. Also, after landing, pronation of a shoe wearer's foot issecurely prevented by the action of the wavy plate 4.

Moreover, in this embodiment, the shock absorbing member is formed ofviscoelastic materials having a higher energy loss, such as 70% or more,or 85% or more. Thus, even when a very high impact load is applied atthe time of jumping, a shock to the shoe heel part immediately aftercontacting the ground is securely absorbed, and compressive deformationand lateral deformation of the upper and lower midsoles 3 a, 3 b afterlanding are securely restrained by the action of the wavy plate 4. Insuch a way, a shoe wearer can exert a sufficient kick power to theground and control activities.

Furthermore, according to this embodiment, since the shock absorbingmember 7 extends along a longer area at the lateral side of the heelpart A than the medial side, a shoe sole structure that is suitable fortracks is achieved. Because, in athletics such as tracks, athletes landon the ground more frequently from the lateral side of the heel portion.

Here, the reason why the elongated length LL of the shock absorbingmember 7 is limited to 0.1L or more is that at least the length of 0.1Lis required to absorb a shock directly after landing from the lateralside. The reason why the elongated length LL is limited to 0.5L or lessis as follows: It is sufficient that the shock absorbing member extendsto the midfoot portion at the longest, and if the shock absorbing memberhas the length over 0.5L, it reaches the forefoot portion. Further, thereason why the elongated length LM is limited to 0.1L or less is that ifthe length is over 0.1L it promotes pronation.

Also, according to this embodiment, as abovementioned, amplitude of awavy configuration of the wavy plate 4 at the heel portion is smaller onthe lateral side and greater on the medial side. That is, moment ofinertia of area of the wavy plate 4 is greater on the medial side, andthus, compressive hardness, which represents hardness to compressivedeformation of the whole midsole, is higher on the medial side.

Therefore, in this case, when a runner lands on the ground from thelateral side of the heel part A during running, the shock absorbingmember 7 on the lateral side absorbs a shock to the outsole directlyafter contacting the ground. And the medial side of the midsole havinggreater compressive hardness sustains leaning of a foot toward themedial side of the heel portion after landing, and thus, lateraldeformation of the heel part A after landing and pronation of a foot isprevented. In such a way, by interaction between the shock absorbingmember 7 and the wavy plate 4, a shock applied to the shoe heel partdirectly after contacting the ground is effectively absorbed andpronation of a shoe wearer's foot is securely prevented.

Alternative Embodiment 1

In the above-mentioned embodiment, a running shoe has been taken as anexample, but the present invention can also be applied to a shoe otherthan a running shoe

For example, in the case of a tennis shoe or a basketball shoe as shownin FIGS. 4A and 5A, medially and laterally extending portions LM and LLof the shock absorbing member 7 are reversed as compared to the runningshoe. And as shown in FIGS. 6A and 7A, the amplitudes AM and AL of themedial and lateral sides of the wavy plate 4 are also reversed ascompared to the running shoe. That is,

0.1L≦LM≦0.5L, LL≦0.1L, AM<AL

In this case, the shock absorbing member 7 is provided along a longerregion at a medial side than at a lateral side. Such a sole structure issuitable for a tennis shoe or a basketball shoe because tennis orbasketball players move more often in the lateral direction and land onthe ground more frequently from the medial side of the heel portion.

Here, the reason why the elongated length LM of the shock absorbingmember is limited to 0.1L or more is that at least the length of 0.1L isrequired to absorb a shock directly after landing from the medial side.The reason why the elongated length LM is limited to 0.5L or less is asfollows: It is sufficient that the shock absorbing member extends to themidfoot portion at the longest, and if the shock absorbing member hasthe length over 0.5L, it reaches the forefoot portion. Further, thereason why the elongated length LL is limited to 0.1L or less is that ifthe length is over 0.1L it promotes supination.

Furthermore, in this case, amplitude of a wavy configuration of the wavyplate 4 at the heel portion is smaller on the medial side and greater onthe lateral side. That is, moment I of inertia of area of the wavy plate4 is greater on the lateral side and smaller on the medial side, andthus, compressive hardness, which represents hardness to compressivedeformation of the whole midsole, is higher on the lateral side.

Consequently, in this case, when a tennis or basketball player lands onthe ground from the medial side of the heel part A during a game, theshock absorbing member 7 on the medial side absorbs a shock to theoutsole directly after contacting the ground. The lateral side of themidsole having greater compressive hardness sustains leaning of a foottoward the lateral side of the heel portion after landing. Thus, lateraldeformation of the heel part A after landing is prevented and supinationof a shoe wearer's foot is prevented. In such a way, by interactionbetween the shock absorbing member 7 and the wavy plate 4, a shockapplied to the shoe heel portion directly after contacting the ground iseffectively absorbed and supination of a shoe wearer's foot is securelyprevented.

Alternative Embodiment 2

The present invention can further be applied to a shoe such as a walkingshoe, which strikes onto the ground more often from a generally centralportion of a shoe heel part on a rear end side. In this case, as shownin FIGS. 4B, 5B, 6B, and 7B,

0.1L≦LL≦0.15L, 0.1L≦LM≦0.15L, AM≈AL

Here, LM and LL are medially and laterally extending portions of theshock absorbing member 7, respectively. AM and AL are amplitudes of themedial and lateral sides of the wavy plate 4, respectively.

In this case, both extending portions of the shock absorbing member 7 onthe medial and lateral sides do not need to be different from eachother, and they are set to be nearly the same length.

Here, the reason why each of the elongated lengths LL and LM of theshock absorbing member 7 is limited to 0.1L or more is that at least thelength of 0.1L is required to absorb a shock directly after landing fromthe rear central portion of the heel portion. The reason why theelongated lengths LL and LM are 0.15L or less is as follows: It issufficient that the shock absorbing member has a length of 0.15L at thelongest to absorb a shock applied to the rear central portion of theheel portion.

In this case, since a shoe wearer lands on the ground from the rearcentral portion of the heel portion, pronation or supination hardlyoccurs. Thus, it is not necessary to alter amplitude of a wavyconfiguration between the medial side and the lateral side of the heelportion of the wavy plate, and amplitudes between the medial and thelateral sides are made nearly equal.

As explained above in greater detail, according to the sole structure ofthe athletic shoe of the present invention, a shock applied to the shoeheel part directly after landing is effectively absorbed and pronationor supination of a shoe wearer's foot can be securely prevented. Thesole structure of the present invention is useful for athletic shoes,such as running shoes, tennis shoes, basketball shoes, walking shoes, orthe like.

Those skilled in the art to which the invention pertains may makemodifications and other embodiments employing the principles of thisinvention without departing from its spirit or essential characteristicsparticularly upon considering the foregoing teachings. The describedembodiments and examples are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. Consequently, while the invention has been described withreference to particular embodiments and examples, modifications ofstructure, sequence, materials and the like would be apparent to thoseskilled in the art, yet fall within the scope of the invention.

What is claimed is:
 1. A sole structure of an athletic shoe comprising:an upper midsole that is formed of a soft elastic material and thatextends from a heel portion of said sole structure to a forefoot portionof said sole structure; a lower midsole that is formed of a soft elasticmaterial and that is disposed at least at a part of said heel portionunder at least a part of said upper midsole; a wavy plate that isprovided between said upper midsole and said lower midsole and that hasa wavy configuration at least at said heel portion and progressing to amidfoot portion of said sole structure; an outsole fitted to a bottomsurface of said lower midsole; and a shock absorbing member that isformed of a viscoelastic material having at least 70% energy loss, andthat is arranged in said heel portion between said wavy plate and saidoutsole and extending from a rearmost end of said heel portion to a rearedge of said lower midsole in said heel portion.
 2. The sole structureof claim 1, wherein said viscoelastic material has 85% or more energyloss.
 3. The sole structure of claim 2, wherein said shock absorbingmember has a hardness of H_(A)C on an Asker C scale, said hardness ofH_(A)C satisfying an inequality, H_(A)C≦55.
 4. The sole structure ofclaim 3, wherein said shock absorbing member is shaped as a curved stripthat extends along an outer perimeter of said heel portion at saidrearmost end, and said curved strip has a width of 10 mm or more.
 5. Thesole structure of claim 2, wherein said shock absorbing member is shapedas a curved strip that extends along an outer perimeter of said heelportion at said rearmost end, and said curved strip has a width of 10 mmor more.
 6. The sole structure of claim 5, wherein there existinequalities, 0.1L≦LL≦0.5L and LM≦0.1L; where L is an entire length of ahorizontal projection plane of said outsole, LL is a length of alaterally extending portion of said shock absorbing member, said lengthLL being measured from said rearmost end of said heel portion along ashoe elongated direction, and LM is a length of a medially extendingportion of said shock absorbing member, said length LM being measuredfrom said rearmost end of said heel portion along said shoe elongateddirection.
 7. The sole structure of claim 6, wherein an amplitude of awavy corrugation of said wavy plate at said heel portion is smaller onthe lateral side and greater on the medial side.
 8. The sole structureof claim 5, wherein there exist inequalities, LL≦0.1L and 0.1L≦LM≦0.5L;where L is an entire length of a horizontal projection plane of saidoutsole, LL is a length of a laterally extending portion of said shockabsorbing member, said length LL being measured from said rearmost endof said heel portion along a shoe elongated direction, and LM is alength of a medially extending portion of said shock absorbing member,said length LM being measured from said rearmost end of said heelportion along said shoe elongated direction.
 9. The sole structure ofclaim 8, wherein an amplitude of a wavy corrugation of said wavy plateat said heel portion is smaller on the medial side and greater on thelateral side.
 10. The sole structure of claim 5, wherein there existinequalities, 0.1L≦LL≦0.15L and 0.1L≦LM≦0.15L; where L is an entirelength of a horizontal projection plane of said outsole, LL is a lengthof a laterally extending portion of said shock absorbing member, saidlength LL being measured from said rearmost end of said heel portionalong a shoe elongated direction, and LM is a length of a mediallyextending portion of said shock absorbing member, said length LM beingmeasured from said rearmost end of said heel portion along said shoeelongated direction.
 11. The sole structure of claim 10, whereinamplitude of a wavy configuration of said wavy plate at said heelportion is generally equal between a medial side and a lateral side. 12.The sole structure of claim 2, wherein there exist inequalities,0.1L≦LL≦0.5L and LM≦0.1L; where L is an entire length of a horizontalprojection plane of said outsole, LL is a length of a laterallyextending portion of said shock absorbing member, said length LL beingmeasured from said rearmost end of said heel portion along a shoeelongated direction, and LM is a length of a medially extending portionof said shock absorbing member, said length LM being measured from saidrearmost end of said heel portion along said shoe elongated direction.13. The sole structure of claim 2, wherein there exist inequalities,LL≦0.1L and 0.1L≦LM≦0.5L; where L is an entire length of a horizontalprojection plane of said outsole, LL is a length of a laterallyextending portion of said shock absorbing member, said length LL beingmeasured from said rearmost end of said heel portion along a shoeelongated direction, and LM is a length of a medially extending portionof said shock absorbing member, said length LM being measured from saidrearmost end of said heel portion along said shoe elongated direction.14. The sole structure of claim 13, wherein an amplitude of a wavycorrugation of said wavy plate at said heel portion is smaller on themedial side and greater on the lateral side.
 15. The sole structure ofclaim 2, wherein there exist inequalities, 0.1L≦LL≦0.15L and0.1L≦LM≦0.15L; where L is an entire length of a horizontal projectionplane of said outsole, LL is a length of a laterally extending portionof said shock absorbing member, said length LL being measured from saidrearmost end of said heel portion along a shoe elongated direction, andLM is a length of a medially extending portion of said shock absorbingmember, said length LM being measured from said rearmost end of saidheel portion along said shoe elongated direction.
 16. The sole structureof claim 15, wherein amplitude of a wavy configuration of said wavyplate at said heel portion is generally equal between a medial side anda lateral side.
 17. The sole structure of claim 1, wherein said shockabsorbing member has a hardness of H_(A)C on an Asker C scale, saidhardness of H_(A)C satisfying an inequality, H_(A)C≦55.
 18. The solestructure of claim 17, wherein said shock absorbing member is shaped asa curved strip that extends along an outer perimeter of said heelportion at said rearmost end, and said curved strip has a width of 10 mmor more.
 19. The sole structure of claim 1, wherein said shock absorbingmember is shaped as a curved strip that extends along an outer perimeterof said heel portion at said rearmost end, and said curved strip has awidth of 10 mm or more.
 20. The sole structure of claim 19, whereinthere exist inequalities, 0.1L≦LL≦0.5L and LM≦0.1L; where L is an entirelength of a horizontal projection plane of said outsole, LL is a lengthof a laterally extending portion of said shock absorbing member, saidlength LL being measured from said rearmost end of said heel portionalong a shoe elongated direction, and LM is a length of a mediallyextending portion of said shock absorbing member, said length LM beingmeasured from said rearmost end of said heel portion along said shoeelongated direction.
 21. The sole structure of claim 20, wherein anamplitude of a wavy corrugation of said wavy plate at said heel portionis smaller on the lateral side and greater on the medial side.
 22. Thesole structure of claim 20, wherein an amplitude of a wavy corrugationof said wavy plate at said heel portion is smaller on the lateral sideand greater on the medial side.
 23. The sole structure of claim 12,wherein an amplitude of a wavy corrugation of said wavy plate at saidheel portion is smaller on the lateral side and greater on the medialside.
 24. The sole structure of claim 19, wherein there existinequalities, LL≦0.1L and 0.1L≦LM≦0.5L; where L is an entire length of ahorizontal projection plane of said outsole, LL is a length of alaterally extending portion of said shock absorbing member, said lengthLL being measured from said rearmost end of said heel portion along ashoe elongated direction, and LM is a length of a medially extendingportion of said shock absorbing member, said length LM being measuredfrom said rearmost end of said heel portion along said shoe elongateddirection.
 25. The sole structure of claim 24, wherein an amplitude of awavy corrugation of said wavy plate at said heel portion is smaller onthe medial side and greater on the lateral side.
 26. The sole structureof claim 19, wherein there exist inequalities, 0.1L≦LL≦0.15L and0.1L≦LM≦0.15L; where L is an entire length of a horizontal projectionplane of said outsole, LL is a length of a laterally extending portionof said shock absorbing member, said length LL being measured from saidrearmost end of said heel portion along a shoe elongated direction, andLM is a length of a medially extending portion of said shock absorbingmember, said length LM being measured from said rearmost end of saidheel portion along said shoe elongated direction.
 27. The sole structureof claim 26, wherein amplitude of a wavy configuration of said wavyplate at said heel portion is generally equal between a medial side anda lateral side.
 28. The sole structure of claim 1, wherein there existinequalities, 0.1L≦LL≦0.5L and LM≦0.1L; where L is an entire length of ahorizontal projection plane of said outsole, LL is a length of alaterally extending portion of said shock absorbing member, said lengthLL being measured from said rearmost end of said heel portion along ashoe elongated direction, and LM is a length of a medially extendingportion of said shock absorbing member, said length LM being measuredfrom said rearmost end of said heel portion along said shoe elongateddirection.
 29. The sole structure of claim 1, wherein there existinequalities, LL≦0.1L and 0.1L≦LM≦0.5L; where L is an entire length of ahorizontal projection plane of said outsole, LL is a length of alaterally extending portion of said shock absorbing member, said lengthLL being measured from said rearmost end of said heel portion along ashoe elongated direction, and LM is a length of a medially extendingportion of said shock absorbing member, said length LM being measuredfrom said rearmost end of said heel portion along said shoe elongateddirection.
 30. The sole structure of claim 29, wherein an amplitude of awavy corrugation of said wavy plate at said heel portion is smaller onthe medial side and greater on the lateral side.
 31. The sole structureof claim 1, wherein there exist inequalities, 0.1L≦LL≦0.15L and0.1L≦LM≦0.15L; where L is an entire length of a horizontal projectionplane of said outsole, LL is a length of a laterally extending portionof said shock absorbing member, said length LL being measured from saidrearmost end of said heel portion along a shoe elongated direction, andLM is a length of a medially extending portion of said shock absorbingmember, said length LM being measured from said rearmost end of saidheel portion along said shoe elongated direction.
 32. The sole structureof claim 31, wherein amplitude of a wavy configuration of said wavyplate at said heel portion is generally equal between a medial side anda lateral side.
 33. The sole structure of claim 1, wherein an amplitudeof a wavy corrugation of said wavy plate at said heel portion is smalleron the lateral side and greater on the medial side.